Inflator second stage combustion control

ABSTRACT

A new type of airbag inflator that may be used in an airbag system is disclosed. The inflator will generally include a housing and two initiators. Accordingly, the inflator is a “dual-stage” inflator. The two stages are disposed within the housing. The second initiator is disposed within a second stage generant cup. A cap is also used to engage the second stage cup. The cap maintains seated engagement with the second stage cup, even during deployment of the second stage. The second stage will also include one or more perforations, which constitute openings through which gas may flow. When the second initiator is in the unactuated state, these perforations will be isolated from the generant by the cap. Actuation of the second initiator unseals the one or more perforations but does not unseat the cap from the cup, due to constraints put in place to prevent such unseating.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/287,843 filed on Nov. 28, 2005. This prior application isincorporated herein by this reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to airbag inflators. More specifically,the present invention is a new type of airbag dual-stage inflator thatmay be used with vehicle airbag systems.

2. Description of the Prior Art

Vehicle airbag systems are known in the art and have been credited withgreatly increasing the overall safety of motor vehicles. Specifically,these airbag systems are designed such that during an accident, one ormore airbags will be rapidly inflated and will be positioned between thevehicle occupant and the hard surfaces of the vehicle interior. Theseinflated airbags will inhibit the vehicle occupant from impacting theinterior surfaces of the vehicle and will thus greatly reduce thelikelihood that the occupant will experience significant injuries in thecrash.

As is known in the art, airbag systems will generally include aninflator that is capable of rapidly producing a large quantity of gas.As its name implies, the purpose of the inflator is to “inflate” theairbag. When an accident occurs, the inflator will rapidly produce alarge quantity of gas that is then channeled into the airbag. In turn,such rapid influx of gas inflates and expands the airbag and causes theairbag to become positioned in front of one or more of the interiorsurfaces of the vehicle. As accidents occur quickly, this inflation ofthe airbag must occur very rapidly—i.e., generally within approximately100 or 150 milliseconds.

Many currently known inflators are referred to as “dual-stage” inflatorsin that these devices contain two separate chambers that containgenerant to be ignited separate from each other. Examples of these typesof dual-stage inflators are disclosed in the followings patents (whichpatents are expressly incorporated herein by reference): U.S. Pat. No.6,364,353; U.S. Pat. No. 6,142,515; U.S. Pat. No. 6,315,322; and U.S.Pat. No. 6,701,849. As explained in these patents, these dual-stageinflators are designed such that if the vehicle experiences aless-severe, less-dangerous crash, the initiator in the first chamberwill be signaled and will be used to inflate the airbag. However, if amore serious crash is experienced such that the airbag needs to beinflated at a more rapid rate and/or to a greater peak pressure, thenboth the first chamber and the second chamber will be used to inflatethe airbag.

Unfortunately, there are significant problems associated with currentlyknown dual-stage inflators (such as the type disclosed in theabove-referenced patents). Specific types of pyrotechnic dual-stageinflators are designed such that the second stage contains a supply ofgas generant that is combusted to form a quantity of inflation gas.However, at the time that this combustion occurs in the second chamber,the internal pressure within the inflator has already been dissipatedand brought back down to ambient (atmospheric) pressure (or nearatmospheric pressure).

The combustion of the second initiator's gas generant at atmosphericpressure creates significant disadvantages. For example, such combustionat atmospheric pressure generally results in incompletecombustion/reaction of the gas generant. This incomplete combustion isundesirable in that it results in the formation of undesirable effluentsor side-products. Vehicle manufacturers have determined that inflatorsproducing such undesirable effluents may not be used in certain airbagapplications. Likewise, in this situation, the late second chambercombustion will not produce gas rapidly enough to provide late eventrestraint of the occupant (which may be desirable in certainapplications).

Accordingly, it would be an advancement in the art to produce a new typeof dual-stage inflator that addresses these problems. More specifically,it would be an advancement to create a new dual-stage inflator that doesnot produce these undesirable effluents and may be used in all types ofairbag applications. Such a device is disclosed herein.

BRIEF SUMMARY OF THE INVENTION

The present embodiments relate to an airbag system that may be used on avehicle interior. Like other airbag systems, this present systemincludes an airbag to inflate in front of the vehicle occupant in theevent an accident or crash occurs, thereby protecting the occupant andpreventing the occupant from harmfully impacting a portion of thevehicle interior.

The airbag system will generally include an inflator that is capable ofproducing a large quantity of gas that will be used to inflate theairbag. The inflator contains two separate chambers or stages—namely afirst stage and a second stage. A sensor will also be use with theairbag system. The sensor communicates with a controller and is designedto detect when the vehicle is experiencing a crash. Accordingly, in theevent that the sensor detects a crash, the sensor signals thecontroller, which in turn, causes the inflator to inflate the airbag.

In addition to detecting the occurrence of a crash, the sensor alsodetects the severity of the crash. If the sensor determines that theseverity of the crash is above a first predetermined threshold level,the sensor will so indicate to the controller. Likewise, if the sensordetermines that the severity of the crash is above a secondpredetermined threshold level—the second predetermined level beinggreater than the first—then the sensor will indicate to the controllerthat a more serious and significant crash is occurring.

The severity of the crash that is detected by the sensor will determinehow the airbag is inflated. Specifically, if the severity of the crashis only above the first threshold level, then the controller willinflate the airbag using only the first stage. However, if the severityof the crash is determined to be above the second threshold level, thecontroller will inflate the airbag using both the first stage and thesecond stage.

In the event that only the first stage is actuated by the controller,the airbag will be inflated without the use of the second stage. In sucha situation, the gas generant housed in the second stage will remain inthe solid, undeployed state. Generally, this will be accomplished byhaving a first initiator ignite and/or convert gas generant stored inthe inflator into a quantity of inflation gas. Such actuation of thefirst stage will also unseal the inflator such that the inflation gascreated by the first stage may exit the inflator and enter the airbag.

In the event that both the first stage and the second stage are used todeploy the airbag, embodiments may be constructed in which the firststage actuates prior to actuation of the second stage. Otherembodiments, however, may be constructed in which both the first stageand the second stage are actuated at the same time.

The second stage that is used as part of the present embodiments has agenerant cup. This cup is generally used to house a quantity of gasgenerant. A cap is also used in conjunction with the cup and engages thecup in seated engagement. Taken together, the generant cup and the capforms a chamber that is sealed. Accordingly, the gas generant within thegenerant cup is kept in a sealed environment.

Unlike many previously known systems, the cap associated with the secondstage includes one or more perforations. These perforations are holesthrough which gas or air may pass. However, when the second stage is inthe undeployed, unactuated state, the perforations will be sealed by therelative positions of the cup and the cap.

If the second stage receives the actuation signal from the controller,the second stage will ignite/combust the gas generant housed within thegenerant cup. Such ignition/combustion of the gas generant pushesoutwardly on all surfaces on the cap. This force upon the cap will notfully unseat the cap from the generant cup due to controls in place forthis purpose. However, such force will cause the cap to displace fromits relative position with the generant cup. In turn, this displacementof the cap exposes the perforations in the cap to the second stage loadand allows the inflation gas produced by the ignition of the gasgenerant to escape the cup. Once the inflation gas has left the cup, theinflation gas may be combined with the inflation gas produced by thefirst stage and may be used to inflate the airbag.

It should be noted however that even after the perforations becomeexposed to the second stage, the pressure maintained within theinitiator cup is greater than atmospheric pressure due to thecontrolling influence of the perforations. Accordingly, when the gasgenerant within the cup combusts, this combustion occurs at high/optimalpressures rather than atmospheric/ambient pressure.

Other embodiments of the present invention may also be constructed suchthat the perforations associated with the second-stage are located onthe generant cup rather than the cap. Accordingly, when the gas generantis combusted within the second-stage, the produced inflation gas willpush against the generant cup and cap to expose the perforations. Inturn, displacement of the cup and cap from their relative pre-combustionpositions unseals the perforations and allows the inflation gas toescape out from the interior of the cup.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order that the manner in which the above-recited and other featuresand advantages of the invention are obtained will be readily understood,a more particular description of the invention briefly described abovewill be rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 is a cutaway sectional view of a vehicle interior which includesan airbag system according to the present embodiments;

FIG. 2 is a schematic view of the airbag system of FIG. 1;

FIG. 3 is sectional view of an inflator according to the presentembodiments, wherein the inflator is shown in the unactuated position;

FIG. 4 is a sectional view of the inflator of FIG. 3 in which only theinflator's first initiator has been actuated;

FIG. 5 is a sectional view of the inflator of FIG. 3 in which both thefirst initiator and the second initiator have been actuated;

FIG. 6A is a sectional view of a second embodiment of an inflator thatmay be used in conjunction with the present airbag system showing bothstages in the unactuated position; and

FIG. 6B is a sectional view of the inflator of FIG. 6A in which the boththe first stage and the second stage have been actuated.

FIG. 7A is a sectional view of another embodiment of an inflator inwhich both stages are shown in the unactuated position;

FIG. 7B is a sectional view of the inflator of FIG. 7A in which bothstages have been actuated;

FIG. 8A is a sectional view of an additional embodiment of an inflatorin which both stages are shown in the unactuated position;

FIG. 8B is a perspective sectional view of the inflator of FIG. 8A;

FIG. 8C is a sectional view of the inflator of FIG. 8A in which in whichboth stages have been actuated;

FIG. 8D is a perspective sectional view of the inflator of FIG. 8C;

FIG. 9A is a sectional view of another embodiment of an inflator inwhich both stages are shown in the unactuated position; and

FIG. 9B is a sectional view of the inflator of FIG. 9A in which bothstages have been actuated;

DETAILED DESCRIPTION OF THE INVENTION

The presently preferred embodiments of the present invention will bebest understood by reference to the drawings, wherein like parts aredesignated by like numerals throughout. It will be readily understoodthat the components of the present invention, as generally described andillustrated in the figures herein, could be arranged and designed in awide variety of different configurations. Thus, the following moredetailed description of the embodiments of the present invention, asrepresented in the Figures, is not intended to limit the scope of theinvention, as claimed, but is merely representative of presentlypreferred embodiments of the invention.

Referring now to FIG. 1, a cutaway sectional view of an example of avehicle interior 10 is illustrated. The vehicle interior 10 includes adashboard 12, an occupant seat 14, a steering wheel 16, and a steeringcolumn 18. The steering column 18 operates to support the steering wheel16 and connect the steering wheel 16 to the dashboard 12. A vehicleoccupant 20 is also shown on the vehicle interior 10. The vehicleoccupant 20 is seated on the occupant seat 14.

As is known in the art, an airbag system 30 is included within thevehicle interior 10. The airbag system 30 includes an inflatablerestraint 32 (shown in phantom) that is designed to inflate in the eventof an accident or crash. More specifically, as shown in FIG. 1, theinflatable restraint 32 is an airbag designed such that if a crashoccurs, the inflatable restraint (or airbag) 32 will inflate in front ofthe occupant 20 and inhibit the occupant 20 from harmfully impacting thesteering wheel 16, the steering column 18, the dashboard 12, or otherportions of the vehicle interior 10.

It should be noted that the airbag system 30 shown in FIG. 1 is a“steering wheel” airbag system in that the airbag 32 is designed suchthat it will inflate from the steering wheel 16 and will protect thevehicle driver in the event of a crash. However, this illustration ismade for illustrative purposes only. Those of skill in the art willrecognize that embodiments of the airbag system 30 could also beimplemented as part other types of vehicular airbag systems. Forexample, the airbag system 30 could also be implemented (either in wholeor in part) as a passenger airbag system, an overhead airbag system, aknee airbag system, knee-bolsters, a side-curtain airbag system, aglove-box airbag system, a dashboard airbag system, inflatable seatbelts, etc.

The airbag system 30 shown in FIG. 1 also includes an inflator 34. Thisinflator will be described in greater detail below. The inflator 34 is adevice that is capable of producing a large quantity of gas that will beused to inflate the airbag 32.

A sensor 36 may also be added to the airbag system 30. This sensor 36 isa device that is known in the art and is designed to sense/detect whenthe vehicle is experiencing a crash. Usually, the sensor 36 detects thiscrash by sensing impact, measuring the deceleration of the vehicle, orsensing any of a variety of known physical parameters. The sensor 36 maybe attached to a controller 38, which is a microcomputer or other typeof processing device. This controller 38 is designed such that if thesensor 36 detects a crash, the controller 38 will process a signalreceived from the sensor 36 and will cause the inflator 34 to producethe quantity of inflation gas necessary to inflate the airbag 32.

Referring now to FIG. 2, a schematic view illustrates the generaloperation of the airbag system 30. If the sensor 36 detects that a crashis occurring, the sensor 36 will determine the severity of the crash orimpact. If the severity of the impact is determined to be at or above afirst predetermined threshold level, the sensor 36 indicates thissituation to the controller 38. The first threshold level of crashseverity is a level at which inflation of the airbag 32 at a relativelylow rate is desired for protection of a vehicle occupant 20 (shown inFIG. 1). If the vehicle condition sensed by the crash sensor 36 is at orabove a second predetermined threshold level, it indicates theoccurrence of an impact having a second, higher, predetermined thresholdlevel of severity. The second threshold level of impact severity is alevel at which inflation of the airbag 32 at a relatively high rate isdesired for protection of a vehicle occupant 20.

As shown in FIG. 2, the inflator 34 includes a first initiator 50. Thefirst initiator 50 is designed such that it is capable of initiatingproduction of a quantity of inflation gas from a first inflation source54. Generally, this first inflation source 54 is a gas generant materialthat will produce a quantity of gas if ignited. Accordingly, the firstinitiator 50 operates to produce the quantity of inflation gas byigniting the gas generant.

The inflator 34 is designed such that if the sensor 36 senses that theimpact is above the first threshold level, the controller 38 will send asignal to the inflator 34 that causes the first initiator 50 to ignitethe first inflation source 54 and produce the inflation gas. Thisinflation gas will then be channeled into the airbag 32 to inflate theairbag 32.

The inflator 34 shown in FIG. 2 also includes a second initiator 58 thatis capable of initiating production of a quantity of inflation gas froma second inflation source 60. Again, this second inflation source 60 isa gas generant material that will be ignited by the second initiator 58to produce a quantity of gas if ignited. In some embodiments, the firstand second inflation sources 54, 60 will comprise the same material. Ofcourse, other embodiments may be constructed in which the material usedfor the first inflation source 54 differs from the material used for thesecond inflation source 60.

In the event that the sensor 38 determines that the severity of theimpact is above the second threshold level which is greater than thefirst threshold level, the sensor 38 will send an appropriate signalindicating this condition to the controller 38. Upon receipt of thissignal, the controller 38 will send a signal to the inflator 34 thatcauses both the first initiator 50 and the second initiator 58 to ignitethe respective inflation sources 54, 60. This ignition of both the firstand the second inflation sources 54, 60 produces greater quantities ofinflation gas that will inflate the airbag 32 at a relatively higherrate in order to provide the occupant 20 with greater protection duringthis impact.

Referring now to FIG. 3, a sectional view illustrates an embodiment ofthe inflator 34 in greater detail. As will be described herein ingreater detail, the inflator 34 is a dual-stage inflator that comprisestwo separate chambers or stages that may be deployed separately (orsimultaneously) to inflate an airbag. For background information onother types of known dual-stage inflations, the reader may consult thefollowing patents: U.S. Pat. No. 6,364,353; U.S. Pat. No. 6,142,515;U.S. Pat. No. 6,315,322; and U.S. Pat. No. 6,701,849 (which patents areincorporated herein by reference).

The inflator 34 may comprise a housing 70. This housing 70 is generallycylindrical in shape and is made of metal (such as aluminum or stainlesssteel) or another suitable material. This housing will generallycomprise an upper wall 72 (which is sometimes referred to as a“diffuser”). The housing also includes a lower wall 74 (which issometimes called a “base”). The upper wall 72 may be “domed,” that is,the wall 72 has a curved configuration that projects away from the lowerwall 74. Likewise, the lower wall 74 may also be “domed”—i.e.,configured with a curved configuration that projects away from the upperwall 72.

The upper wall 72 and the lower wall 74 are connected by side walls 80.One or more inflation outlets 84 are disposed in a circular array on theside walls 80. Each one of the inflation fluid outlets 84 extendsradially through the side wall 80. As will be explained in greaterdetail below, the outlets 84 enable flow of inflation fluid out of theinflator 34 to inflate the airbag 32. One or more filters (not shown)through which air may pass can also be positioned in front of theoutlets 84. These filters are designed to filter the inflation gas thatexits the inflator 34. Other features known in the art, such as heatsinks (not shown) that are designed to cool the inflation gas as itexits the inflator 34, may also be included as part of the inflator 34.

The housing 70 comprises two openings 90, 92 that are disposed along thelower wall 74. These openings 90, 92 provide a space through whichelectrical terminals 94 on the first initiator 50 and the secondinitiator 58 may be attached to electrical wires (not shown). As isknown in the art, these terminals 94 are connected, via the electricalwires, which are capable of supplying an electrical current into theinitiators 50, 58. More specifically, when the controller 38 sends thesignal to the inflator 34 to deploy, electrical current will be sent toone or more of the initiators 50, 58, thereby causing the initiators 50,58 to ignite the inflation sources 54, 60.

The first inflation source 54 is positioned proximate the firstinitiator 50. The first initiator 50 is positioned within a firstchamber 111. (As explained in greater detail herein, this first chamber111 comprises the first stage of the inflator 34). In the embodimentshown in FIG. 3, the first inflation source 54 is a solid gas generant55. As will be explained in greater detail below, the inflator 34 isdesigned such that the first inflation source 54 constitutes the “firststage” of the dual stage inflator 34. In other words, during an accidentor crash, the first inflation source 54 will be ignited/combusted toproduce a first stage of inflation gas that may be used to inflate theairbag 32.

As shown in FIG. 3, a generant cup 110 (which may also be referred to asthe “second generant cup” or “second stage cup”) is used in conjunctionwith the second initiator 58. This generant cup 110 comprises one ormore walls that are designed to create a second chamber 112 that housesthe second inflation source 60. (The second chamber 112 is sometimesreferred to as the “second stage” or “second generant chamber”). In someembodiments, the second chamber 112 will also house all or a portion ofthe second initiator 58. As is known in the art, the second inflationsource 60 may comprise solid gas generant 61. In many embodiments, thesecond gas generant 61 and the first gas generant 55 will be composed ofthe same material. Of course, other embodiments may have the second gasgenerant 61 be composed of a different material than that which is usedto make up the first gas generant 55.

A cap 120 is also used in conjunction with the second initiator chamber112. This cap 120 is described in greater detail herein. As can be seenin FIG. 3, the cap 120 engages the second generant cup 110 in seatedengagement with the second generant cup 110. The cap 120 operates toseal and enclose the second chamber 112. Generally, the cap 120 will bepress fit onto the cup 110 to ensure that the chamber 112 is sealed.

In the embodiment shown in FIG. 3, the cap 120 includes one or moreperforations 124. The size and number of the perforations 124 willdepend upon the particular embodiment. These perforations 124 are holesor openings that have been formed into the cap 120. However, as shown inFIG. 3, the cap 120 is designed such that when the second initiator 58is in the non-actuated state, the perforations 124 are isolated from thesecond stage (i.e., closed) by the relative position of cap 120 to thecup 110. Accordingly, even with the perforations 124, the second chamber112 is a sealed chamber.

Referring now to FIG. 4, a sectional view illustrates the inflator 34during actuation of the first stage. Specifically, in FIG. 4, thecontroller 38 (not shown) has received a signal from the sensor 36 thatthe vehicle is experiencing a crash in which the severity of the impactis above the first threshold level. Accordingly, the controller 38 hassent the appropriate signal to the inflator 34 causing actuation of thefirst initiator 50.

Upon receipt of the appropriate signal from the sensor 36, thecontroller 38 causes an electrical current to be sent to the terminals94 that are located on the first initiator 50. (However, in thissituation, no electrical current is sent to the second initiator 58.)This influx of current into the first initiator 50 deploys the firststage of the inflator 34 by igniting/combusting the first inflationsource 54/gas generant 55. Such ignition/combustion of the firstinflation source 54/gas generant 55 creates a quantity of inflation gasat a pressure of 1,000 to 4,000 psi (or more). Once the first inflationsource 54/gas generant 55 has been converted into a quantity ofinflation gas, this gas may then be channeled out of the inflator 34(via the outlets 84) into the airbag 32.

It should be noted that prior to ignition/combustion of the firstinflation source 54, the first stage of the inflator 34 is maintained ina sealed condition so that the inflation source 54 can combust at a highpressure (and so that none of the inflation source 54 will leak out ofthe inflator 34). Accordingly, when the first inflation source 54 isdeployed, such deployment will also have the effect of unsealing thefirst stage such that gas may flow out of the inflator 34. Such“unsealing” of the inflator 34 may be accomplished in a variety of ways,as is known in the art, including blowing a seal, moving/deforming theupper wall 72 so that a fluid path is exposed, removing a lid/barrierthat seals the inflator, etc. Of course, other means for unsealing theinflator 34 may also be used.

It should be noted however, that the actuation of the first initiator 50does not affect the second initiator 58. Rather, the second initiator 58and the second inflation source 60 remain sealed by the cap 120 andremains unreacted—i.e., in the solid state.

Referring now to FIG. 5, a sectional view illustrates the inflator 34during actuation of the inflator 34 in the event that the sensor 36 hasdetected a crash in which the severity of the impact is greater than thesecond predetermined level. As noted above, the second threshold levelis greater than the first threshold level. Accordingly, when the sensor36 signals to the controller 38 that the severity of the impact is at orabove the second threshold level, the controller 38 knows that thisimpact is more serious (and potentially more dangerous) than an impactwhich severity is only at the lower, first threshold level.

Upon receipt of the signal from the sensor 36, the controller 38 willsend the appropriate signal to the first initiator 50 and will cause thefirst initiator 50 to actuate in the manner discussed above in FIG. 4.(For purposes of brevity, this discussion will not be repeated).However, unlike the situation in FIG. 4, the controller 38 will alsocause the second initiator 58 to actuate. In some embodiments, thisactuation of the second initiator 58 will occur at the same time as theactuation of the first initiator 50. In other embodiments, the secondinitiator 58 will be actuated after actuation of the first initiator 58.Other embodiments may be constructed in which the second initiator 58will begin actuation while the first initiator 50 is undergoingactuation—i.e., the first initiator 50 will begin the actuation processand then a short time later (5 milliseconds, 10 milliseconds, 20milliseconds, 100 milliseconds etc.) the second initiator 58 will beginits actuation process.

In order to begin the actuation process, an electrical current will beintroduced into the second initiator 58 via the electrical terminals 94.This influx of current into the second initiator 58 ignites the secondinflation source 60/gas generant 61 that is housed within the secondchamber 112. As is known in the art, this ignition of the secondinflation source 60/gas generant 61 creates a quantity of inflation gas.

Once formed, the inflation gas housed on the interior of the secondinitiator chamber 112 pushes outwardly against the walls of the chamber112. Unlike many previously known inflator systems, the production ofthe inflation gas from the second inflation source 60 does not cause thecap 120 to separate from the second cup 110. Rather, at all times duringcombustion/actuation of the second initiator 58, the cap 120 remains inseated engagement with the second initiator cup 110 due to constraintsthat are designed for this purpose (which will be described herein).However, the produced inflation gas does exert an outward force upon thecap 120 which causes the cap 120 to displace outwardly. In turn, thisoutward displacement of the cap 120 unseals and/or exposes the one ormore perforations 124. Such unsealing of the perforations 124 means thatthe inflation gas on the interior of the second initiator chamber 112may escape from the second initiator chamber 112 by passing through theperforations 124. Once this quantity of gas has passed through theperforations 124, this gas mixes with other inflation gas formed fromthe first inflation source 54/gas generant 556 and then flows out of theinflator 34 via the outlets 84 (in the manner described above).

As can be seen in FIG. 5, the deployment of the second initiator 58 willcause the cap 120 to displace and expose the perforations 124. In theembodiment shown in FIG. 5, the cap 120 will move outwardly until itabuts/contacts the upper wall 72, at which point, the upper wall 72 willrestrict/prevent further movement of the cap 120. In this manner, theupper wall 72 prevents the cap 120 from being completely unseated fromthe cup 110. Of course, other embodiments may use other mechanisms forensuring that the cap 120 does not unseat from the cup 110 includingslots, hooks, engagement means, interlocking features, and/or any otherfeature capable of restricting the cap 120 from unseating from the cup110.

It should be noted however, that the use of this cap 120 andperforations 124 provides significant advantages that are not availablewith previously known inflator systems. Specifically, as describedabove, one of the problems associated with known dual-initiatorinflators is that combustion of the gas generant in the second stageusually occurs at atmospheric (ambient) pressure when fired at a delayedcondition, which ultimately results in incomplete combustion of the gasgenerant, undesirable effluents, etc. The inflator 34 of the presentembodiments does not suffer from these problems. Rather, in the inflator34, combustion of the second inflation source 60 occurs within a closed,pressurized chamber 112 which is maintained at pressures that aregreater than (or even much greater than) atmospheric pressure due to thecontrolling influence of the perforations 124 (and that the cap 120 doesnot unseat from the cup 110). Accordingly, when the second inflationsource 60 is combusted, it will be completely burned at a high pressureand will not have high levels of undesirable effluents.

Referring now to FIG. 6A, a second embodiment of an inflator 34 aaccording to the present invention is illustrated. The inflator 34 a issimilar to the inflator 34 that was described above in conjunction withFIGS. 1-5. (For purposes of brevity, the above-recited description willnot be repeated.) Rather, only the differences between this embodimentand the inflator 34 will be highlighted.

As can be seen in FIG. 6A, the first initiator 50 is used in conjunctionwith a first chamber 111 and the first inflation source 54 is housedoutside of the first chamber 111. However, in other respects, the firstinitiator 50 will actuate and deploy the first stage of the inflator 34a in the manner outlined above. Of course, those of skill in the artwill recognize how to implement and create an inflator 34 a having afirst chamber 111 that is used in conjunction with the first initiator50.

The main difference between the inflator 34 a shown in FIG. 6A and theinflator 34 discussed above relates to the second initiator 58 and willbe discussed in greater detail below.

Unlike the inflator 34, the inflator 34 a does not comprise a system inwhich the second generant cup 110 has a cap 120 that contains one ormore perforations 124. Rather, in the inflator 34 a, the perforations124 a are actually added to the second stage generant cup 110 a.However, as shown in FIG. 6A, the perforations 124 a are indeed sealedby the cap 120 a in that the cap 120 a holds the generant cup 110 a inthe proper position such that the perforations 124 a remaincovered/sealed.

Referring now to FIG. 6B, a sectional view illustrates the inflator 34 aas the second initiator 58 is being actuated. As shown in FIG. 6B, thecombustion of the second inflation source 60 produces a quantity ofinflation gas that exerts an outward force on the cap 120 a and thesecond cup 110 a. In turn, this exertion of force on the cap 120 a thatexposes the perforations 124 a and allows inflation gas to exit out ofthe chamber 112. In some embodiments, this may be accomplished by havingthe cap 120 a move outward such that the perforations 124 a becomeexposed. Again, it should be noted however, that such movement of thecap 120 a will not unseat the cap 120 a from the cup 110 a. Rather, thecap 120 a will displace until it contacts the upper wall 72 of theinflator 34 a, at which point, the upper wall 72 will restrict furthermovement of the cap 120 a. Of course, other controlling features thatwill prevent the cap 120 a from unseating from the cup 110 a duringmovement may also be used.

Referring now to FIG. 7A, an additional embodiment of the presentinvention is illustrated. FIG. 7A shows an inflator 34 b that is similarto the inflators 34, 34 a discussed above. As shown in FIG. 7A, theinflator 34 b comprises a first chamber 111 that is used in conjunctionwith the first initiator 50. This first chamber 111 will house aquantity of gas generant 55. Another supply of gas generant 126 is alsopositioned outside of the first chamber 111. Depending upon theembodiment, the gas generant 55 and the gas generant 126 may comprisethe same material or may comprise different materials. Taken together,the gas generant 55 and the gas generant 126 constitute the firstinflation source 54. Accordingly, the first initiator 50 will operate todeploy the first stage of the inflator 34 b by igniting/combusting thefirst inflation source 54 (i.e., the gas generants 55 and 126) in themanner described above.

As with the previous embodiment, the main difference between theinflator 34 b and the previously described inflators relates to the cap120 b and the generant cup 110 b that is used to house the secondinflation source 60. Specifically, this embodiment shows another type ofcap 120 b and cup 110 b that may be used. The generant cup 110 b issealed by the cap 120 b. Perforations 124 b are also provided. Theseperforations are positioned on the cup 110 b rather than on the cap 120b.

Referring now to FIG. 7B, a sectional view illustrates the inflator 34 bas the second initiator 58 is being actuated. As with the previousembodiments, the actuation of the second initiator 58 will combust thesecond inflation source 60 (FIG. 7A) and will displace the cap 120 b.This displacement of the cap 120 b will expose and/or unseal theperforations 124 b in the cup 110 b such that the gas produced by thesecond inflation source 60 may be used to inflate the airbag 32. As withthe previous embodiments, controls are put into place to ensure that themovement of the cap 120 b will not operate to unseat the cap 120 b fromthe cup 110 b. Rather, the cap 120 b will move until it abuts and/orcontacts the upper wall 72 of the inflator 34 b, and at that point,further movement of the cap 120 b will be restricted so that the secondstage may be deployed at a high/optimal pressure (as described above).

Referring now to FIGS. 8A and 8B, an additional embodiment of aninflator according to the present invention is illustrated. FIGS. 8A and8B are sectional views that illustrates an inflator 34 c that is similarto the embodiments described previously. Specifically, the features andelements associated with the first stage and the first initiator 50 thatare shown in FIG. 8A is similar and/or identical to that which wasdescribed above. However, with respect to the second stage, theembodiment shown in FIG. 8A includes a different type of generant cup110 c that is sealed by a cap 120 c.

The generant cup 110 c has a lip 121 that is designed such that it willreceive and hold the cap 120 c. In this embodiment, the cap 120 ccomprises a plug or barrier that will fit on the inside of the cup 110c. The lip 121 will hold the cap 120 c in place and will prevent the cap120 c from moving inwardly toward the second initiator 58. As shown inboth FIGS. 8A and 8B, one or more perforations 124 c are positioned onthe cup 120 c. In the present embodiment, the perforation 124 c is aslot or other opening. Generally, the perforation 124 c is positionedabove the lip 121. Accordingly, when the cap 120 c is positioned againstthe lip 121, the cap 120 c will seal the perforation 124 c.

Referring now to FIGS. 8C and 8D, the inflator 34 c is shown as thesecond initiator 58 is actuated. As with the previous embodiments,actuation of the second stage of the inflator 34 c will causecombustion/ignition of the second inflation source 60. In turn, thisignition of the inflation source 60 will cause the cap 120 c todisplace. In the embodiment shown in FIGS. 8C and 8D, the cap 120 c willdisplace outwardly such that the cap 120 c moves past the perforation124 c. In turn, such movement of the cap 120 c unseals/exposes theperforation 124 c and allows inflation gas to flow out of the secondchamber 112.

As with the previous embodiments however, such displacement of the cap120 c does not cause the cap 120 c to unseat from the cup 110 c. Rather,the cap 120 c will displace and move outwardly until it contacts theupper wall 72. Once such contact with the upper wall 72 is made, theabutment between the upper wall 72 and the cap 120 c will preventfurther movement of the cap 120 c and will allow the second chamber 112to remain pressurized for optimal combustion/ignition of the secondinflation source 60 (as described above).

Referring now to FIG. 9A, a further embodiment of an inflator 34 d ofthe present invention is illustrated. The inflator 34 d has a firstchamber 111 and a first stage that is similar to that which is shownabove in inflator 34 b. However, the cap 120 d and the generant cup 110d found in the second stage of the inflator 34 d differ from that whichis shown above.

Like some of the embodiments shown above, the cap 120 d is designed suchthat it will be positioned over the top of the cup 110 d. One or moreperforations 124 d are positioned on the cup 110 d and on the cap 120 d.However, because of the position of the relative positions of both thecup 110 a and the cap 120 d, the perforations 124 d are sealed by thecap 120 d when the inflator 34 d is in the undeployed, unactuatedposition.

Referring now to FIG. 9B, the inflator 34 d is shown as the secondinitiator 58 is actuated. As with the previous embodiments, actuation ofthe second initiator 58 causes outward movement of the cap 120 d. In theembodiment shown in FIG. 9B, this outward movement of the cap 120 ddisplaces the cap 120 d into a position in which the perforations 124 dare unsealed/exposed. As such, the inflation gas created by thecombustion of the second inflation source 60 may exit the second chamber112 by passing through the perforations 124 d. At the same time however,this displacement of the cap 120 d does not operate to unseat the cap120 d from the cup 120 due to constraints in place that are designed forthis purpose. Rather, when the cap 120 d is displaced, the cap 120 dwill abut with the upper wall 72 of the inflator 34 d and will bemaintained in a position that will allow the combustion of the secondinflation source 60 to occur at a high/optimal pressure.

As explained above, the above-described embodiments are designed suchthat the actuation of the second stage will displace the cap as a meansof exposing/unsealing the perforations. It should be noted, however,that other embodiments may be designed such that actuation of the secondinitiator causes the generant cup to displace (and expose theperforations) rather than the cap. For example, embodiments may beconstructed in which the actuation of the second initiator operates toexpose the perforations by causing the cup to displace and/or slide offits base. In other embodiments, a portion of the cup and/or the cap maydisplace to expose the perforations. In yet further embodiments, boththe cap and the cup may displace to expose the perforations. Those withskill in the art will recognize that any type of movement that operatesto expose the perforations in the cup 110 a may be used in theseembodiments.

The present embodiments also provide a method of making an airbag system30. This method involves the step of obtaining an airbag 32 andobtaining an inflator.

The inflator used in the present method may either be any of theinflators described herein. Further, the method also involves the stepof obtaining a sensor 36 that measures the severity of the vehicularimpact.

The present invention may be embodied in other specific forms withoutdeparting from its structures, methods, or other essentialcharacteristics as broadly described herein and claimed hereinafter. Thedescribed embodiments are to be considered in all respects only asillustrative, and not restrictive. The scope of the invention is,therefore, indicated by the appended claims, rather than by theforegoing description. All changes that come within the meaning andrange of equivalency of the claims are to be embraced within theirscope.

1. An airbag system comprising: an airbag; an inflator comprising: ahousing; a first chamber disposed within the housing; a generant cup anda cap disposed within the housing, the generant cup and the cap defininga second chamber that houses gas generant, the cap engaging the generantcup in seated engagement; one or more perforations located on thegenerant cup and the cap, wherein because of the position of therelative positions of both the cup and the cap, the one or moreperforations on both the cap and the cup are sealed by the cap when theinflator is undeployed and actuation of gas generant in the secondchamber unseals the one or more perforations permitting inflation gas toescape the second chamber without unseating the cap from the generantcup; and a sensor that detects the severity of an impact such that ifthe sensor detects that the severity of the impact is above a firstthreshold, the inflator actuates gas generant in the first chamber. 2.An airbag system as in claim 1, wherein if the sensor detects that theseverity of the impact is above a second threshold level greater thanthe first threshold level, the inflator actuates gas generant in boththe first chamber and the second chamber.
 3. An airbag system as inclaim 1, wherein the pressure of the second chamber during actuation ofthe gas generant is maintained at a pressure that is greater thanatmospheric pressure.
 4. An inflator for inflating an airbag comprising:a housing; a first chamber disposed within the housing; a generant cupand a cap disposed within the housing, the generant cup and the capdefining a second chamber that houses gas generant, the cap engaging thegenerant cup in seated engagement; and one or more perforations locatedon the generant cup and on the cap, wherein because of the position ofthe relative positions of both the cup and the cap, the perforations onboth the cap and the cup are sealed by the cap when the inflator isundeployed, wherein actuation of gas generant in the second chamberunseals the one or more perforations without unseating the cap from thegenerant cup.
 5. An inflator as in claim 4 wherein the pressure of thesecond chamber during actuation of the gas generant is maintained at apressure that is greater than atmospheric pressure.
 6. An inflator as inclaim 4, wherein the first chamber comprises a inflation source, whereinactuation of the first initiator comprises ignition of the inflationsource.